A Presidential candidate wishing to be on the Presidential Preference Primary ballot must pay a filing fee of $2,500 or file a petition with 10,000 signatures from registered voters.
The filing fee or signatures are due January 25,2020
It isn't clear whether these signatures have to come from registered “affiliated” voters, or if they can come from any registered voter.
State law allows Parties to decide whether they allow “unaffiliated” voters to vote in their primaries. It is probably best to register to vote as “affiliated” with the Republican Party.